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Journal Cover Composites Science and Technology
  [SJR: 1.512]   [H-I: 144]   [186 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0266-3538
   Published by Elsevier Homepage  [3089 journals]
  • The combination of π-π interaction and covalent bonding can
           synergistically strengthen the flexible electrical insulating
           nanocomposites with well adhesive properties and thermal conductivity
    • Abstract: Publication date: 8 February 2018
      Source:Composites Science and Technology, Volume 155
      Author(s): Zheng Su, Hua Wang, Konghu Tian, Weiqi Huang, Chao Xiao, Yulan Guo, Jing He, Xingyou Tian
      Adding thermal conductive filler is an effective method to improve the thermal conductivity of polymer matrix. In this research, we demonstrated that the polymer composites with much improved thermal conductivity while maintaining low electrical conductivity, which could be achieved via using hybrid 2D stacked filler and controlling the alignment of the filler in polymer matrix. In order to do this, the graphene oxide (GO) was prepared and simultaneously reduced/functionalized by diethylenetriamine (DETA) to obtain NH2-functionalized graphene (NfG) which designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via π-π stacking interaction. In this situation, since the NfG sheets were fixed on the surface of h-BN, the NfG sheets were well separated from each other and participated in the resin curing process. Hence, not only significantly enhanced thermal conductivity (∼3.409 W/m·K, in-plane direction) was obtained, but also a very low electrical conductivity was achieved. The low electrical conductivity was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated NfG sheets via π-π stacking interaction. In addition, the nanocomposites also exhibited good thermal stability and adhesive properties. We believed that this special structure will provide a new thought for fabricating thermal interface materials (TIMs) with much high thermal conductivity as well as low electrical conductivity.

      PubDate: 2017-12-13T07:58:40Z
       
  • Hyperbranched polyether epoxy grafted graphene oxide for benzoxazine
           composites: Enhancement of mechanical and thermal properties
    • Abstract: Publication date: 8 February 2018
      Source:Composites Science and Technology, Volume 155
      Author(s): Xin Wang, Nan Li, Jinyan Wang, Guiyang Li, Lishuai Zong, Cheng Liu, Xigao Jian
      Hyperbranched polyether epoxy (HBPEE) grafted graphene oxide (GO-HE) was designed to improve the dispersion/exfoliation and interfacial interaction between graphene oxide and benzoxazine (BOZ). The structures and morphologies of graphene oxide (GO) and GO-HE sheets were characterized by FT-IR, XRD, XPS, Raman spectroscopy, TEM and AFM. BOZ composites containing GO and GO-HE were prepared with different loadings and systemically investigated. GO and GO-HE produced 88% and 139% improvements, respectively, in impact strength at 0.05 wt% loading. The three-point bending test indicated that the BOZ/GO-HE composites exhibited higher flexural strength and modulus than the neat BOZ or BOZ/GO composites. For BOZ composites containing 0.05 wt% GO-HE, the flexural strength increased by 14.4%, and the flexural modulus increased by 10.0% compared to that of neat BOZ. Furthermore, the Tg and thermal stability of BOZ/GO-HE composites were significantly improved compared to those of neat BOZ and BOZ/GO composites. These improvements can be ascribed to better dispersion of GO-HE and a stronger interfacial interaction between GO-HE and the matrix, according to TEM and SEM analyses.

      PubDate: 2017-12-13T07:58:40Z
       
  • Damage initiation in unidirectional fiber composites with different
           degrees of nonuniform fiber distribution
    • Abstract: Publication date: 8 February 2018
      Source:Composites Science and Technology, Volume 155
      Author(s): Sarah A. Elnekhaily, Ramesh Talreja
      This paper reports a study of the initiation of the first failure event in unidirectional composites subjected to transverse tension. Two energy based point failure criteria – critical dilatational energy density and critical distortional energy density – are considered. The manufacturing induced disorder in the fiber distribution in the composite cross section is described in terms of the degree of nonuniformity, which is quantified and for which an algorithm is developed. The nonuniformity is captured in a representative volume element (RVE) whose minimum size is determined based on statistics of nearest fiber distance distribution. Several realizations of the RVE for three fiber volume fractions and three degrees of nonuniformity are analyzed using a finite element model. A parametric study of the effect of matrix/fiber stiffness ratio on the damage initiation is also conducted. Significant effects of the fiber distribution nonuniformity on the strain to onset of damage are found.

      PubDate: 2017-12-13T07:58:40Z
       
  • Temperature driven failure of carbon epoxy composites – A
           quantitative full-field study
    • Abstract: Publication date: 8 February 2018
      Source:Composites Science and Technology, Volume 155
      Author(s): P.R. Wilson, A.F. Cinar, M. Mostafavi, J. Meredith
      Aerospace composites are exposed to low temperatures that induce high levels of stress within the material. This is sufficient to induce fractures and eventually delaminations and failure. Thus, understanding how these temperature induced translaminar fractures can be reduced is an important area of research. This work investigates cross-ply unidirectional (UD) and woven (W) carbon fibre laminates with MTM46 epoxy to assess how the cure schedule (low temperature, LTC and high temperature, HTC) effect temperature driven fractures. A novel digital image correlation technique was applied to determine in-situ fracture progression versus temperature. Thermal techniques investigated the degree of cure, resin plasticity, thermal expansion and beta transition effects. The cure schedule for carbon epoxy laminates has a marked effect on quantity of manufacturing induced fractures and the temperature at which temperature induced internal fracture occurs. This work has demonstrated that a lower temperature cure is more robust against temperature driven fracture despite having a larger coefficient of thermal expansion (CTE) and similar levels of plasticity. Low temperatures induce high internal stresses but the residual stress resulting from high temperature cure is of greater concern. DIC is an excellent method to determine onset and progression of translaminar fracture as well as the behaviour of composite materials subject to temperature effects. This work is of great benefit when considering the design of CFRP structures subject to low temperature loading, furthermore the data can be used to more accurately model this phenomena in future.

      PubDate: 2017-12-13T07:58:40Z
       
  • Non-contact percolation of unstable graphene networks in
           poly(styrene-co-acrylonitrile) nanocomposites: Electrical and rheological
           properties
    • Abstract: Publication date: 8 February 2018
      Source:Composites Science and Technology, Volume 155
      Author(s): Chong Gao, Peng Liu, Yanfen Ding, Tao Li, Feng Wang, Juan Chen, Shimin Zhang, Zengxi Li, Mingshu Yang
      Poly (styrene-co-acrylonitrile) (SAN)/chemically reduced graphene oxide (CRG) nanocomposites were prepared using a coagulation method. Due to the presence of SAN molecules that prevented CRG sheets from aggregation during reduction, CRG sheets were dispersed homogeneously in SAN. The electrical and rheological properties of the nanocomposites were systematically investigated to elucidate the structure of CRG electrical and rheological networks. With the incorporation of CRG sheets, both the electrical and rheological properties of the nanocomposites were remarkably changed. At higher CRG concentrations, the nanocomposites became electrically conductive and exhibited solid-like behaviors. According to the scaling power law, the electrical networks were constructed at a percolation threshold of 0.17 vol % compared to the rheological networks at 0.10 vol %. This discordance is attributed to the intrinsic difference in the network structure. Though both electrical and rheological networks were constructed through a non-contact mode, the rheological networks required SAN chains as bridges, while electrical networks did not. The CRG networks showed instabilities in both physical and chemical structure. Upon thermal annealing at 190 °C, the networks underwent self-improvement through disordering and thermal reduction of CRG sheets.

      PubDate: 2017-12-13T07:58:40Z
       
  • Layer-by-layer grafting CNTs onto carbon fibers surface for enhancing the
           interfacial properties of epoxy resin composites
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Min Zhao, Linghui Meng, Lichun Ma, Lina Ma, Xiaobing Yang, Yudong Huang, Jong Eun Ryu, Akash Shankar, Tingxi Li, Chao Yan, Zhanhu Guo
      An effective method for bonding carbon nanotubes (CNTs) onto carbon fibers (CFs) surface via layer-by-layer (LBL) grafting method is reported here. The CNTs have been chemically grafted as confirmed by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) indicates that this LBL method can increase the dispersion quality of the CNTs on CF surface. The polarity, wettability and roughness of the CFs have been significantly increased after the CNTs modifying. The interfacial shear strength (IFSS) and impact strength test suggest that the hierarchical structure can result in a remarkable improvement for the interfacial properties. The results also indicate that this LBL method is a promising technique to modify CFs with the high interfacial performance.

      PubDate: 2017-12-13T07:58:40Z
       
  • Constructing a double-percolated conductive network in a carbon
           nanotube/polymer-based flexible semiconducting composite
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Wei Liu, Yuanyi Yang, Min Nie
      Conductive polymer composites featuring double-percolated network structures have attracted widespread interest. Constructing such a structure and controlling the trans-phase migration of the conductive filler remain the main challenges for the application of these conductive polymer composites. In this study, we report a novel two-step “in situ microfibrillation” and “microfiber coalescence” strategy that includes melt-drawing and a compressive annealing process to achieve a stable, double-percolated network of a polybutene-1 (PB-1)/polystyrene (PS)/multiwalled carbon nanotubes (MWCNTs) ternary system. Triggered by the compressive annealing treatment, inter-fiber coalescence led to the formation of an interconnected network, resulting in excellent conductive performance (volume resistivity down to 4.6 × 103  Ω · cm ) with a MWCNT dosage as low as 1 wt%. Surface energy calculations and experimental evidence both indicated that the selective distribution of the MWCNTs in the PS phase resulted from the preferential surface wetting behavior and π-π interactions between the MWCNTs and PS, which also immobilized the MWCNTs, even at elevated temperatures. This work established a facile and scalable technology for constructing double-percolated structures in multiphase systems, thus providing access to intriguing functionalities and applications.

      PubDate: 2017-12-13T07:58:40Z
       
  • An experimental investigation of the temperature effect on the mechanics
           of carbon fiber reinforced polymer composites
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Zian Jia, Tiantian Li, Fu-pen Chiang, Lifeng Wang
      Carbon fiber reinforced polymer (CFRP) composites are increasingly used in civil, naval, aerospace, and wind energy applications, where they can be frequently exposed to harsh temperature conditions and under static and dynamic loads. The extreme temperature conditions and dynamic loading are critical for CFRP composites structural design as the constituent polymer properties are highly sensitive to temperature and strain rate. This work experimentally investigates the effect of temperature, ranging from −100 °C to 100 °C, on the mechanical properties of CFRP composites under static and dynamic three-point bending tests. The results reveal that CFRP composites provide enhanced flexural strength, maximum deflection, and energy absorption at lower temperatures (−60 °C, −100 °C) while relatively poor performance at a higher temperature (100 °C). Experimental images from the post-mortem photographs, scanning electron microscopy, and high speed videos are implemented to observe various failure behaviors including microbuckling, kinking, and fiber breakage at different temperatures. Analytical modeling is further applied to reveal the underlying mechanisms responsible for these temperature dependent mechanical behaviors. The findings reported here provide insights into the study of the temperature effect on the mechanical response of CFRP composites, which expands the way to design stiffer, stronger and tougher CFRP composites.

      PubDate: 2017-12-13T07:58:40Z
       
  • Porous graphene-polyaniline nanoarrays composite with enhanced interface
           bonding and electrochemical performance
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Huitao Yu, Guoxiang Xin, Xin Ge, Chaoke Bulin, Ruihong Li, Ruiguang Xing, Bangwen Zhang
      There are ever increasing interests in three dimensional (3D) graphene for the construction of wearable electrics and flexible energy storage devices. Herein, we report a 3D porous graphene supported polyaniline (PANI) nanoarrays composite with enhanced interface bonding and high load fraction of PANI for supercapacitor application. We demonstrate that by utilizing benzenesulfonic acid functionalization followed by a pre-immersion treatment, surface chemistry and permeability of the porous graphene can be improved significantly, which favors the controllable growth of high-quality PANI nanoarrays. The resulting composite used as a freestanding electrode exhibits excellent electrochemical performance, hence a maximum specific capacitance of 752 F/g with retention of 90.8% over 10000 cycles was achieved.

      PubDate: 2017-12-13T07:58:40Z
       
  • Strain pattern detection of composite cylinders using optical fibers after
           low velocity impacts
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Bo-Hun Choi, Il-Bum Kwon
      The strain pattern distributed on composite cylinders after impacts was detected using optical fibers for the first time. The sensing optical fiber was implemented on the composite cylinders using aluminum (Al)-coated optical fiber, polyimide-coated optical fiber, or standard single mode fiber (SSMF) of polymer-coating. The residual strain of this sensing fiber was measured by a Brillouin optical correlation domain analysis (BOCDA) sensor system, using phase modulation and single side band modulation methods. Impact events of 10, 20, and 40 J energies as barely visible impact damages (BVID) were applied on the cylinders, and these fibers were deployed on the cylinder surface, or were embedded in the cylinders. For the surface deployment, Al-coated fiber exhibited the highest residual strain due to Al plastic deformation, and the strain was three times higher than the lowest SSMF value. For the embedment deployment, these fibers were individually embedded in the cylinder, which was composed of sixteen carbon fiber reinforced polymer layers using a filament winding process. In contrast to the surface deployment, the embedded SSMF gave as high residual strain as that of the Al-coated fiber. These similar residual strains of the three embedded optical fibers suggested that they came from permanent material damage inside the material. Impact events with fiber embedment caused the optical signal in the Al-coated fiber to suffer serious additional insertion loss, but the SSMF did not show loss. So the general fiber for optics communications was successfully demonstrated as a distributed residual strain sensor to detect BVID impacts of composite materials. The strain values were maintained for at least 15 months after impact events. This residual strain sensor is economical, because special fibers like Al-coated fiber were not needed, and the sensor is efficient, because it could sense the strain for long distance, without additional impact-driven insertion loss.

      PubDate: 2017-12-13T07:58:40Z
       
  • Excellent electrically conductive PE/rGO nanocomposites: In situ
           polymerization using rGO-Supported MAO cocatalysts
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): He-xin Zhang, Jae-Hyeong Park, Keun-Byoung Yoon
      Superior electrically conductive PE nanocomposites were prepared with reduced graphene oxide(rGO)-supported MAO cocatalyst via in situ ethylene polymerization. The electrical conductivity of the composites was very high at 1.2 S/m. This value is the highest among reported rGO-filled composites. The cocatalyst system was prepared by modifying with alkoxysilane compound to prevent restacking of the GO plane in the reduction process and solvothermal reduction of GO. The effect of cocatalysts on the properties of nanocomposites and distribution of nanosheets in the polymer matrix was investigated in detail. The mechanical properties and thermal stability of PE/rGO nanocomposites were significantly increased via the addition of a small amount of rGO. These properties resulted from the restacked rGO layers exfoliated in situ by the ethylene insertion between the intercalated layers.

      PubDate: 2017-12-13T07:58:40Z
       
  • Modeling and analysis of nonlinear elastoplastic behavior of
           compatibilized polyolefin/polyester/clay nanocomposites with emphasis on
           interfacial interaction exploration
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Seyed Mohammad Reza Paran, Mohammad Abdorahimi, Azadeh Shekarabi, Hossein Ali Khonakdar, Seyed Hassan Jafari, Mohammad Reza Saeb
      Analysis of mechanical properties of compatibilized polymer pairs comprising clay nanoplatelets was the subject of numerous works, however nonlinear elastoplastic behavior of such nanocomposites has rarely been addressed in the literature. Though localization of nanofiller within one or at the interface of two phases was occasionally dealt with, there often were serious complexities with the lack of knowledge about the interface region. This work focuses on modeling of stress-strain behavior of the compatibilized polyolefin/polyester/clay nanocomposites to give some more lights on the interfacial interaction in such complex system, and clay localization analysis. The use of two kinds of organomodified clays as well as two compatibilizers having different chemical affinity to polymers, and using different amount of compatibilizers led to localization of clay either in the polyester or at the polyolefin/polyester interface region, as confirmed by X-ray diffraction, transmission electron microscopy and uniaxial tensile strength measurements. The mechanical properties analyses revealed a rise in both Young's modulus and tensile strength of composites with clay loading. Application of Bergström-Boyce model brought about a deeper understanding of the effect of compatibilizer and organoclay on large deformation mechanical behavior of polyolefin/polyester/clay nanocomposites. Overall, theoretical analyses could appropriately predict nonlinear elastoplastic behavior of nanocomposites, even though some deviations were detected at yielding and necking regions.

      PubDate: 2017-12-13T07:58:40Z
       
  • Investigation into Mode II interlaminar fracture toughness characteristics
           of flax/basalt reinforced vinyl ester hybrid composites
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): F.A. Almansour, H.N. Dhakal, Z.Y. Zhang
      In this work, the influence of water absorption of flax and flax/basalt hybrid laminates is presented with the aim to investigating the Mode II interlaminar fracture toughness. Four types of composite laminates namely, neat vinyl ester (neat VE), flax fibre reinforced vinyl ester (FVE), flax fibre hybridised basalt unstitched (FBVEu) and flax hybridised basalt stitched (FBVEs), were fabricated by vacuum assisted resin infusion technique. Three-point-end-notched flexure (3ENF) tests were performed to evaluate the critical Mode II strain energy release rate (GIIC) and the crack length (R-curve) at dry and wet conditions, by using two data reduction methods. The morphology of delamination and the fracture shear failure of composite laminates were evaluated using scanning electron microscopy (SEM) and X-ray micro computed tomography (μCT). The results obtained that the fracture energy of FBVEu composites, GIIC init. and GIIC prop. were increased by 58% and 21%, respectively compared to that of FVE dry specimens. Moisture absorption phenomenon caused increasing in the ductility of matrix that improved the resistance to crack initiation. However, this was inverted to a reduction in the fibre/matrix interfacial strength of FBVEu wet composites and a deterioration in the delamination resistance to crack propagation. The critical strain energy release rate of neat VE increased from 157.84 J/m2 to 239.85 J/m2 with reinforcement of flax fibre composites. The experimental results confirmed that basalt fibre hybridisation enhanced the durability and water repellence behaviour of natural fibre reinforced composites.

      PubDate: 2017-12-13T07:58:40Z
       
  • Interfaces in polyethylene oxide modified cellulose
           nanocrystal - polyethylene matrix composites
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): N.H. Inai, A.E. Lewandowska, O.R. Ghita, S.J. Eichhorn
      The interface between cellulose nanocrystals (CNCs) in thermoplastic matrices is one of the most important issues prohibiting the development of CNC-based polymeric composites prepared via melt processing. In the present work, polyethylene oxide (PEO) was used as a compatibilizer to enhance the interface with a polyethylene matrix. It was found that the composites produced using a PEO compatibilizer possess better overall mechanical properties and a higher degree of crystallinity of the polyethylene than the unmodified samples. An increase in both the tensile strength and modulus of the composites was observed for up to 1.5 wt.% of CNCs; beyond this point no significant increases were observed. When CNCs were added (up to 1.5 wt.%) to the matrix, the crystallization peak of the composites in the DSC thermograms shifted to higher temperatures. The stress-transfer process in the composites was monitored using Raman spectroscopy. Higher Raman band shift rates with respect to tensile strain of a peak corresponding to main chain molecular deformation were observed for the composites produced using the PEO compatibilizer. This demonstrates that stress is transferred from the matrix to the fillers more effectively with the presence of PEO. The simple PEO-modification approach adopted in this study avoids the classical solvent method of production of CNC-based nanocomposites which is not really applicable at an industrial scale.

      PubDate: 2017-12-13T07:58:40Z
       
  • Simultaneously improving flame retardancy and dynamic mechanical
           properties of epoxy resin nanocomposites through layered copper
           phenylphosphate
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Qinghong Kong, Ting Wu, Junhao Zhang, De-Yi Wang
      To improve the flame retardancy of epoxy resin (EP), copper phenylphosphate (CuPP) nanoplates were designed and prepared by mixed solvothermal technique, which were incorporated into EP matrix and fabricated EP/CuPP nanocomposites. The results showed that the product was Cu(HO3PC6H5)2 with appropriate thermal stability, and EP/CuPP nanocomposites displayed excellent catalytic charring performance compared with pure EP. The combustion results indicated that pure EP had no rating and its LOI value was only 23.0%. With incorporation of 4 wt% CuPP, EP/4 wt% CuPP nanocomposites passed the UL-94 V1 rating and the LOI value reached 38.2%. The improved flame retardancy of EP/CuPP nanocomposites was proved by cone calorimeter test, and the peak heat release rate, total smoke production, peak CO production value of EP/4 wt% CuPP nanocomposites dramatically decreased by 51.7%, 52.4% and 47.3%, which were attributed to the formation of hard and condensed residues layers on the surface of EP nanocomposites. Additionally, the incorporation of CuPP improved the dynamic mechanical performance of EP nanocomposites, which may be due to the reinforcement effect of CuPP with rigid structure.

      PubDate: 2017-12-13T07:58:40Z
       
  • Nondestructive functionalization of carbon nanotubes by combining
           mussel-inspired chemistry and RAFT polymerization: Towards high dielectric
           nanocomposites with improved thermal management capability
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Ao Xie, Yuxin Wang, Pingkai Jiang, Shengtao Li, Xingyi Huang
      Interface plays a critical role in determining the electrical properties and thermal management capability of carbon (e.g., nanotubes, graphene) based polymer nanocomposites. The strong interface is usually desirable and realized by forming the covalent interaction between nanocarbon and polymer matrix. However, the pristine properties, such as high electrical and thermal conductivity, of nanocarbon are inevitably deteriorated due to the introduction of lattice defects. In this work, a nondestructive strategy, combining mussel-inspired chemistry and surface initiated reversible addition fragmentation chain transfer (RAFT) polymerization, was developed to prepare lattice defect free interface between carbon nanotubes (CNTs) and epoxy resin. Polydopamine (PDA) was first coated on the CNT surfaces and then polymethyl methacrylate (PMMA) or polyglycidyl methacrylate (PGMA) macromolecular chains were grafted onto PDA encapsulated CNTs, which can result in non-covalent or covalent interface between CNTs and epoxy resin, respectively. It was found that PGMA encapsulated CNTs based epoxy nanocomposites show apparent advantages in increasing dielectric constants and suppressing dielectric loss tangent, as well as enhancing thermal conductivity. This study proves the superiority of the covalent interface formed by nondestructive functionalization in enhancing the dielectric properties and thermal management capability of nanocarbon based polymer composites.

      PubDate: 2017-12-13T07:58:40Z
       
  • Electrical property enhancement by controlled percolation structure of
           carbon black in polymer-based nanocomposites via nanosecond pulsed
           electric field
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Minh Triet Tan Huynh, Hong-Baek Cho, Tsuneo Suzuki, Hisayuki Suematsu, Son Thanh Nguyen, Koichi Niihara, Tadachika Nakayama
      The research group of this study demonstrates how Nanosecond Pulsed Electric Field can be used to tune the localization and formation of conducting carbon black (CB) assembles into linear structures with various thicknesses inside an insulating polymer matrix. The Electrorheology phenomenon of CB assembles in pre-polymer of polysiloxane under application of either DC or nanosecond pulsed electric field was observed utilizing optical microscopy method. Comparing to the typical DC electric field which has a value of 1875 V/mm, the nanosecond pulsed electric field facilities the increase in its electric field strength; generated between two constructed electrodes with a space size of 160 μm, to a value reaching 7500 V/mm. This type of electric field can overcome the voltage breakdown that occurs within the tested materials. The conduction structure of CB forms linear assemblies that anchor the composite film surfaces inside the matrix, which could be developed to much thicker percolation structures over five times by the application control of the nanosecond pulsed electric fields. Furthermore, the formation of vertically upright electrical percolation structures attributed to the remarkable decrease of the electrical resistivity of the resulting composites to 3 order of magnitude compared to the composites with a uniform distribution of filler. The electrorheology phenomenon under pulsed field was also tested by the optical observation method. The thickness as well as the concentration of CB particles were able to be controlled via the increasing in the nanosecond pulsed electric field. The novelty of this study lies in the utilizing of nanosecond pulsed field with a high electric strength that overcomes the electrical breakdown during tuning the carbonaceous filler assemblies. This unique technology is energy saving through fabricating polymer-based conductive materials without using surface modification or increasing the filler content.

      PubDate: 2017-12-13T07:58:40Z
       
  • Influence of fiber characteristics on directed electroactuation of
           anisotropic dielectric electroactive polymers with tunability
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Krishna B. Subramani, Richard J. Spontak, Tushar K. Ghosh
      Dielectric elastomers constitute a technologically important class of stimuli-responsive polymers due primarily to their unique ability to achieve large strains (>300 area%) upon exposure to an external electric field. In most reported cases, actuation strains are measured as dielectric elastomers constrained to a circular test configuration essentially waste energy by undergoing isotropic, rather than directional, electroactuation. Recent independent studies have demonstrated, however, that the addition of relatively stiff fibers to a soft dielectric elastomer matrix promotes more energy-efficient anisotropic mechanical behavior and electroactuation response. In this work, we investigate the effects of fiber strain and mechanical properties on electroactuation in anisotropic dielectric electroactive polymers with tunability (ADEPT) fabricated from an acrylic dielectric elastomer. Increases in fiber loading level and stiffness are observed to enhance both mechanical and electroactuation properties to different extents, and we introduce an electroactuation anisotropic enhancement factor to quantify the ratio of electroactuation to mechanical anisotropy. This factor is determined to vary linearly with fiber concentration for nearly all the different ADEPT composites examined in this study.

      PubDate: 2017-12-13T07:58:40Z
       
  • Comparison of ATH and SiO2 fillers filled silicone rubber composites for
           HTV insulators
    • Abstract: Publication date: Available online 9 December 2017
      Source:Composites Science and Technology
      Author(s): Yang Xue, Xiao-fei Li, Dong-hai Zhang, Hao-sheng Wang, Yun Chen, Yun-fa Chen
      To enhance the electrical and mechanical properties of silicone rubber (SIR) in the field of high-voltage insulation, conventional fillers such as aluminum hydroxide (ATH), fumed silica and precipitated silica have been used for many years. In this work, SIR composites filled with ATH, irregular SiO2 (IS) and sphere SiO2 (SS) were prepared by mechanical blending, and the effects of filler type and filler shape on mechanical, electrical and thermal properties of SIR composites were systematically investigated. Compared with ATH-SIR composites, SS-SIR composite exhibited better electrical and mechanical properties. It showed that the tensile strength of SS-SIR composites was up to 6.6 MPa, which was nearly 2-folded compared to ATH-SIR composite. According to the loss tangent results in combination with tensile fracture surface observation, the interfacial interaction between SiO2 fillers and SIR is stronger than that between ATH and SIR, and the dispersion is better in SiO2 fillers filled SIR composites than that in ATH filled composite. The breakdown strength of ATH-SIR composite is only 18.9 kV mm−1, while those of IS-SIR and SS-SIR composites are 24.9 and 24.8 kV mm−1, respectively. Among the three SIR composites, SS-SIR composite has lowest dielectric permittivity and dielectric loss. Compared with ATH-SIR composite, the SiO2 fillers filled SIR composites have the lower thermal conductivity ranging from 30 °C to 150 °C, but they exhibit the better arc aging resistance due to the good thermal stability and thermal conducting property at high temperature. Moreover, the SS-SIR composite exhibits the better arc aging resistance than IS-SIR composite.

      PubDate: 2017-12-13T07:58:40Z
       
  • Microscopical observations of inter-fibre failure under tension
    • Abstract: Publication date: Available online 9 December 2017
      Source:Composites Science and Technology
      Author(s): Elena Correa, María Inmaculada Valverde, María Luisa Velasco, Federico París
      The numerical study of the inter-fibre failure at micromechanical level predicts the appearance of different stages in the development of this damage mechanism; these studies have also allowed the main features of each stage (such as the interfacial debond length and the kinking angle) to be identified. The development of experimental studies aiming to check the relevance of the aforementioned numerical results is crucial. Based on this, this research focused on the tensile test under different loading levels of specimens manufactured from carbon-epoxy cross-ply symmetrical laminates. The microscopic observation of the 90° layers leads to the analysis of the appearance of the transverse cracks as a function of the load, the identification of the previously numerically predicted stages of the mechanism of damage, the measurement of key parameters and the evaluation of the influence of nearby fibres. A clear connection between the numerical and experimental results has been found.

      PubDate: 2017-12-13T07:58:40Z
       
  • Poly (ether ether ketone) - Silicon carbide composite adhesives for
           elevated temperature applications of stainless steel joints
    • Abstract: Publication date: Available online 9 December 2017
      Source:Composites Science and Technology
      Author(s): Ajay Kumar Kadiyala, Jayashree Bijwe
      In the present work, the performance of a series of adhesives based on poly (ether ether ketone) (PEEK)/reinforced with micro-sized silicon carbide (SiC) particles for metal-metal joints was investigated. The size effect for SiC particles was studied by developing two composite adhesives with 3 wt. % of nanoparticles (NPs) (50–60 nm), and other with an equal amount of microparticles (MPs) (20 μm). The influence of particles on retention of adhesive strength at elevated temperature was studied in detail. The inclusion of MPs increased the bond strength of adhesives almost by 2 times and 15 wt. % was found to be optimum. At elevated temperatures, the adhesive strength decreased for all compositions. Interestingly the adhesive strength of composite adhesive at 300 °C was similar to the adhesive strength of virgin PEEK at ambient temperature. MPs performed better than NPs, which was correlated to agglomeration and shape of particles. SEM studies revealed that inclusion of hard fillers led to crack growth inhibition and resisting shearing during lap shear test of joints.

      PubDate: 2017-12-13T07:58:40Z
       
  • Enhanced thermal conductivity and mechanical property through boron
           nitride hot string in polyvinylidene fluoride fibers by electrospinning
    • Abstract: Publication date: Available online 9 December 2017
      Source:Composites Science and Technology
      Author(s): Dong-Li Zhang, Jun-Wei Zha, Wei-Kang Li, Chao-Qun Li, Si-Jiao Wang, Yongqiang Wen, Zhi-Min Dang
      The electrospun polyvinylidene fluoride (PVDF) based modified boron nitride (m-BN) composite with high thermal conductivity and flexibility mechanical property was successfully fabricated by electrospinning method. The uniform dispersion and ordered orientation of m-BN in the m-BN/PVDF composites form a hot string, denoted as a series of thermal conduction fillers, in the direction of the fiber. Hence, the thermal conductivity of the m-BN/PVDF film could reach to 7.29 W m−1K−1 with the addition of 30 wt% m-BN. Besides, the obtained composites also show improved mechanical properties with the tensile strength of 24.06 MPa, low dielectric permittivity of 2.45 and dielectric loss of 0.0242 @ 103 Hz. Therefore, this work provides a new route to prepare the high thermal conductivity films with potential application as flexible power devices.

      PubDate: 2017-12-13T07:58:40Z
       
  • Evaluation of elastic-plastic response of discontinuous carbon
           fiber-reinforced thermoplastics: Experiments and considerations based on
           load-transfer-based micromechanical simulation
    • Abstract: Publication date: Available online 6 December 2017
      Source:Composites Science and Technology
      Author(s): M. Nishikawa, A. Fukuzo, N. Matsuda, M. Hojo
      The present study investigated nonlinear elastic-plastic stress-strain relationships of discontinuous carbon fiber-reinforced thermoplastics (CFRTPs) using experiments and numerical simulations. In the experiments, we conducted uniaxial tensile tests and three-point bending tests for two types of CF/PA6 (carbon fiber/polyamide 6) specimen: injection-molded specimens with short fiber length and aligned fiber orientation, and compression-molded specimens with long fiber length and random fiber orientation. Comparison of the experiment results indicated that the injection-molded specimens exhibited a nonlinear stress-strain response, while the compression-molded specimens exhibited an almost linear response. These results implied that long discontinuous fibers effectively increased the yielding point of composites, even if the composites had random fiber orientation, which eliminated orientation dependence on mechanical properties of the composites. Furthermore, we attempted to simulate elastic-plastic stress-strain relationships of discontinuous CFRTPs in an effort to understand the effect of the microstructure, including fiber length. For this purpose, we employed fiber-based simulations to deal with the microstructure of fibers and matrix and the constitutive law of the matrix. The simulated results indicated that fiber length influences the nonlinearity of the stress-strain relationships of discontinuous CFRTP composites.

      PubDate: 2017-12-13T07:58:40Z
       
  • Cellulose nanofiber aerogels impregnated with bio-based epoxy using vacuum
           infusion: Structure, orientation and mechanical properties
    • Abstract: Publication date: Available online 6 December 2017
      Source:Composites Science and Technology
      Author(s): Tuukka Nissilä, Sakari S. Karhula, Simo Saarakkala, Kristiina Oksman
      Cellulose nanofiber aerogels were used as preforms that were impregnated with a bio-epoxy resin via a widely used vacuum infusion process. The simple and straightforward nanocomposite processing approach resulted in an almost 70% improvement in the storage modulus of the polymer with only an 11.7 wt% cellulose nanofiber content. The nanofibers were well dispersed in the polymer matrix and the fiber structures were anisotropically aligned. The impregnation time of the aerogels was also significantly lower than that of the more commonly used nanopapers. It was thus shown that environmentally friendly and mechanically robust nanocomposites could be produced by impregnating cellulose nanofiber aerogels with a thermosetting resin using a processing approach that has potential to be scaled up for commercial use.

      PubDate: 2017-12-13T07:58:40Z
       
  • Sensitivity, influence of the strain rate and reversibility of GNPs based
           multiscale composite materials for high sensitive strain sensors
    • Abstract: Publication date: Available online 5 December 2017
      Source:Composites Science and Technology
      Author(s): R. Moriche, A. Jiménez-Suárez, M. Sánchez, S.G. Prolongo, A. Ureña
      The addition of functionalized graphene nanoplatelets (f-GNPs) into the epoxy resin of glass fiber multiscale composite materials creates an electrically conductive network. This electrical network is highly sensitive to strain induced in the material. For this reason, it is a competitive material to be used in structural health monitoring (SHM). Sensitivity of multiscale composite materials is ∼50 under tensile loads and the behavior under compression loads differs, making possible the detection of different load conditions. Independency of the strain rate is related to the enhanced interface between f-GNPs and the epoxy matrix due to functionalization. Additionally, the electrical behavior is reversible without the loss of efficiency in sensorial properties.

      PubDate: 2017-12-13T07:58:40Z
       
  • A linear and large-range pressure sensor based on a graphene/silver
           nanowires nanobiocomposites network and a hierarchical structural sponge
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): Xuchu Dong, Yong Wei, Song Chen, Yong Lin, Lan Liu, Jing Li
      It is challenging to manufacture pressure-sensing materials that possess linearly sensitive regime, high sensitivity, and large-range detection for the development of artificial intelligence products. Herein, a very simple approach is proposed to fabricate piezoresistive sensors based on hierarchical structure sea sponges and composites conductive networks of polydopamine reduced graphene oxides and silver nanowires. The hierarchical structures of porous sea sponges including the contacting of multi-scale porous skeletons and the bending of nodes vary synchronously, resulting in the linear relationship between applied compress strain and resistances, Moreover, the as-prepared pressure sensor exhibits a high sensitivity (S = 0.016 kPa−1 at 0-40 kPa) and a large area detection range (gauge factor = 1.5 at 0-60% strain). The synergetic effect of the composites conductive network endows the sensor with excellent reproducibility (>7000 loading/unloading cycles) and fast response time (<54 ms). In addition, demonstrate various applications of pressure sensor for health monitoring ranging from human leg to foot activities (such as toes on points, Restless Legs Syndrome (RLS) and walking).

      PubDate: 2017-12-13T07:58:40Z
       
  • Effect of electrical stress on glass fiber reinforced polymer used in high
           voltage composite insulator under wet environment
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): Yanfeng Gao, Xidong Liang, Yingyan Liu
      The effect of electrical stress on glass fiber reinforced polymer under wet condition has been investigated in the present study. A specially designed and fabricated test setup was used through which the current passing through the GFRP rod during the test was recorded. Based on the changes in morphology of GFRP rod surface and development trend of current, the degradation process of GFRP rod caused by electrical stress under wet condition was divided into four consecutive stages, namely degradation inception stage, hydrolysis stage, carbonization stage and breakdown stage. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray Photoelectron Spectroscopy (XPS) analyses were employed to provide the physical and chemical properties of GFRP at different stages. The results showed that the degradation process of GFRP caused by electrical stress under wet condition progressively developed in the form of degraded channel, in which the epoxy resin matrix deteriorated significantly. The occurrences of hydrolysis, oxidation, pyrolysis and carbonization of epoxy resin matrix could be observed sequentially in the degradation process of GFRP during the test. With the development of the degradation process of GFRP, the content of epoxy resin matrix continued to decrease and the relative content of highly oxidized carbons (C-O, C=O and O-C=O) in epoxy resin matrix on GFRP surface increased before the carbonization process and then decreased in the carbonization process. The present study is helpful for better understanding of the electrical performance of GFRP used in high voltage composite insulator as well as in other electrical applications.

      PubDate: 2017-12-13T07:58:40Z
       
  • Effect of discontinuities in bamboo fibre reinforced epoxy composites
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): D. Perremans, E. Trujillo, J. Ivens, A.W. Van Vuure
      This paper performs a systematic study of the effect of various unidirectional fibre patterns, ranging from different overlapping lengths of adjacent fibre bundles to a complete randomization of the position of individual fibre ends. The study is benchmarked with the mechanical behaviour of a fully continuous unidirectional bamboo fibre-epoxy composite and will show the feasibility of using UD discontinuous technical bamboo fibres in continuous preforms for high-end composites applications. The study shows that the tensile stiffness is hardly influenced by the discontinuity patterns, while the introduction of randomized fibre end discontinuities (individual fibres with segment length 50 mm) leads to a preservation of 85% of the longitudinal tensile strength in comparison with a UD continuous bamboo fibre composite.

      PubDate: 2017-12-13T07:58:40Z
       
  • Nafion® based hybrid composite membrane containing GO and dihydrogen
           phosphate functionalized ionic liquid for high temperature polymer
           electrolyte fuel cell
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): Jatindranath Maiti, Nitul Kakati, Sung Pil Woo, Young Soo Yoon
      A new hybrid composite proton exchange membrane has been synthesized from dihydrogen phosphate functionalized imidazolium ionic liquid (IL-H2PO4), graphene oxide, and Nafion 117 solution. The chemical structure and thermal stability of the dihydrogen phosphate functionalized imidazolium ionic liquid (IL-H2PO4) have been analyzed by 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The structural, thermal, and surface properties of synthesized membrane have been confirmed by FTIR spectroscopy, X-ray diffraction, TGA, and scanning electron microscopy. The proton exchange membranes have been characterized by their ionic conductivity and unit cell performance. The incorporation of IL-H2PO4 and graphene oxide in the Nafion membrane increases its thermal stability. The ionic conductivity of the membranes increases with temperature and amount of IL-H2PO4. The highest ionic conductivity of 0.061 Scm−1 has been achieved at 110 °C under anhydrous conditions which is 1.3 times higher than that of commercial Nafion 117. The synthesized membrane, Nafion/IL/GO, shows the best unit cell performance with a power density of 0.02 W cm−2, which is 13 times higher than that of the commercial Nafion 117 membrane at 110 °C.

      PubDate: 2017-12-13T07:58:40Z
       
  • Electrochemical performance of nanofibrous highly flexible electrodes
           enhanced by different structural configurations
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): Babak Rezaei, Ahmad Mousavi Shoushtari, Mohammad Rabiee, Lokman Uzun, Anthony P.F. Turner, Wing Cheung Mak
      Due to their unique physicomechanical properties, one dimensional (1D) nanostructured conductive materials offer remarkable potential as a flexible electroactive medium for developing miniaturized electronic devices such as supercapacitors, sensors and actuators. In this work, thin films composed of nanocomposite nanofibers with two different architectures, i.e. whiskered nanofibers (WNFs) and hierarchical-structured nanofibers (H-SNFs), were fabricated and their capability to serve as flexible and bendable electrodes were evaluated. The main difference of these two architectures is how the distributions of the nano-fillers (carboxylated multiwalled carbon nanotubes, CMWNTs) through the nanofibers, i.e. the isotropic and anisotropic arrangements, lead to WNFs and H-SNFs, respectively. The percolation threshold of conduction for the H-SNFs (composed of 0.5 wt% CMWCNTs) and the WNFs (composed of 5 wt% CMWCNTs) were 0.13 S cm−1 and 0.07 S cm−1, respectively. Moreover, according to the electrochemical characterizations, although the WNFs had ten orders of magnitude higher nanotube content, the electroactivity and electron transfer rate of H-SNFs was considerably higher than those of WNFs, so that the cyclic voltammetric peak currents of H-SNFs was approximately 1.6 times higher than that of WNFs. As a proof-of-concept, our results indicate that the structural configuration is a major determinative factor, which can largely dictate the final electrical and electrochemical properties of the nanocomposite nanofibers. The bending durability results showed good electrochemical performance even upon 100 bending cycles with ±120° bending angles (retained 93.4% and 83.3% of the initial peak currents for H-SNFs and WNFs, respectively). These two flexible nanocomposite nanofibrous structures could be promising materials for the development of flexible electrodes for biosensing to energy storage applications.

      PubDate: 2017-12-13T07:58:40Z
       
  • In situ construction of dual-noncovalent bonding to prepare enhanced
           carbon nanotubes/poly(methyl methacrylate) nanocomposites
    • Abstract: Publication date: Available online 2 December 2017
      Source:Composites Science and Technology
      Author(s): Guangda Zhu, Xiang Wang, Yu Jiang, Junping Zheng
      Interfacial interaction between carbon nanotubes (CNTs) and polymer matrix is crucial in preparing high-performance CNTs/polymer composites. In this work, dual-noncovalent bonding was constructed via in situ polymerization to improve the interfacial interaction between CNTs and polymer. Two functional monomers, 2-(methacryloyloxy) ethyltrimethyl ammonium chloride (MTC) and styrene (St), were utilized to copolymerize with methyl methacrylate (MMA) via in situ polymerization, meanwhile, carboxylic CNTs was adsorbed through electrostatic interaction and π-π interaction during the polymerization process. 1H NMR and GPC measurements verified that the successful synthesis of copolymer and its adsorption onto the surface of CNTs, while the enhanced interfacial interactions were confirmed by FTIR and Raman. Compared with neat PMMA, the thermal decomposition temperature and tensile strength of the composites were improved by 40 °C and 55.2%, respectively.

      PubDate: 2017-12-13T07:58:40Z
       
  • Preparation of polymer/graphene oxide nanocomposites by a two-step
           strategy composed of in situ polymerization and melt processing
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Lingyun Zhang, Shuhua Tu, Haitao Wang, Qiangguo Du
      Pickering emulsion-templated polystyrene (PS)/graphene oxide (GO) composite microspheres were successfully prepared using surface-functionalized silica as the stabilizer. These preformed polymer/GO composite microspheres were then melt-blended into polymer matrix to prepare nanocomposite materials in a short minute using HAAKE torque rheometer. Transmission electron microscope (TEM) images of the nanocomposites demonstrate that GO is uniformly dispersed into PS matrix. A significant decrease of coefficient of thermal expansion (CTE) values from more than 150 to 50 ppm/K is realized with the introduction of well-dispersed GO nanosheets. The glass transition temperature (Tg) and the temperature of 5% weight loss (T0.05) are increased by 5 and 17 °C, respectively. Furthermore, the impact energy of the composite sample with a GO loading of 0.86% is 64% greater than that of pure PS, and is nearly twice as high as that of the composite which was prepared by direct melt-blending of surface-modified GO and commercial PS. The tensile strength and elongation at break of the composites are also obviously improved. The work provides an economic and convenient method which eliminates the dispersion problem of GO in polymer matrix to prepare GO-based nanocomposite materials for industrial application on a large scale.

      PubDate: 2017-11-16T02:58:41Z
       
  • Isolation of nanocrystalline cellulose from rice straw and preparation of
           its biocomposites with chitosan: Physicochemical characterization and
           evaluation of interfacial compatibility
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Kaimeng Xu, Can Liu, Kunyong Kang, Zhifeng Zheng, Siqun Wang, Zhenguan Tang, Wenxiu Yang
      In order to develop high value-added rice straw residue biocomposites, nanocrystalline cellulose (NCC) from rice straw and chitosan (CS) were used as two main raw materials, the CS/NCC biocomposites were prepared by an acid hydrolysis-ultrasonic treatment and blending casting. The physicochemical properties and evaluation of interfacial compatibility on CS/NCC biocomposites were characterized by TEM, ZP analyzer, UV-vis, FTIR, SEM, XRD, TG, DSC, electron mechanical instrument and water absorption testing. The results reveal that a uniform rod-like or filamentary structure of NCC from rice straw, with the width distribution concentrated on the range of 10–15 nm and several hundred nanometers in length, can be effectively obtained by a relatively high ultrasonic power treatment with the same acid hydrolysis conditions. The superior interfacial compatibility of CS/NCC biocomposites with excellent tensile strength can be achieved at 5% NCC addition level due to optimal dispersion of NCC, strong hydrogen bonding and potential electrostatic interactions between CS and NCC. Additionally the thermal stability and water absorption of biocomposites increase, while the transparency rate, elongation at break decrease as the increase of NCC addition amount from 0% to 20%.

      PubDate: 2017-11-16T02:58:41Z
       
  • Surface engineering of nanosilica for vitrimer composites
    • Abstract: Publication date: 18 January 2018
      Source:Composites Science and Technology, Volume 154
      Author(s): Zhiwei Huang, Yan Wang, Jing Zhu, Junrong Yu, Zuming Hu
      Vitrimers are a new kind of crosslinked polymers with attractive properties of repairing and reprocessing. It is very important to further improve the physical properties of vitrimers to meet the ever growing demand for high-performance materials. However, the mechanical reinforcement of vitrimer matrix by nanoparticles was always accompanied with hindered topological rearrangement because of the restricted chain mobility. In this paper, epoxy and thiol groups functionalized silica nanoparticles (EP-Silica and SH-Silica) were used as fillers for construction of disulfide based vitrimer composites to investigate the surface chemistry of nanoparticles on mechanical and adaptive properties of vitrimers. It is found that both EP-Silica and SH-Silica showed good mechanical reinforcement because of the covalent bonding with matrix as compared to unmodified silica. Although the mechanical reinforcement of SH-Silica was slightly inferior to that of EP-Silica, the stress relaxation of composite reinforced by SH-Silica was much faster than that of EP-Silica filled composite. As a result, SH-Silica based composite showed higher self-healing efficiency as evidenced by time dependent healing tests. Further improvement in mechanical property of composite with moderately retarded stress relaxation at high loading of SH-Silica was also demonstrated. This work demonstrated the possibility of tuning the mechanical and adaptive properties of vitrimer composites by surface engineering of nanoparticles.

      PubDate: 2017-11-16T02:58:41Z
       
  • Microstructural damage based modelling of thermal conductivity of
           cyclically loaded CFRP
    • Abstract: Publication date: Available online 14 November 2017
      Source:Composites Science and Technology
      Author(s): Chandrashekhar P. Hiremath, K. Senthilnathan, N.K. Naik, Anirban Guha, Asim Tewari
      Thermography is widely used in the damage characterization of the composite materials. Effective thermal conductivity of the damaged composite can be predicted based on the temperature distribution obtained using pulse thermography. In this work, a new equivalent circuit model (ECM), based on thermal resistance of the constituents, was developed to compute longitudinal and transverse thermal conductivity of carbon fiber reinforced polymer (CFRP) composite for given microstructural damage state. The damage state, in terms of fiber breakage and interface debonding, was obtained from fatigue loading of CFRP composite. The thermal conductivity of the composite obtained using ECM was in excellent agreement with finite element simulations. Finally, the transverse conductivity obtained from ECM was linearly proportional to the mean grey scale obtained from IR thermography. This is for the first time that an observed thermal property (IR thermography) was correlated to an independently modeled thermal property (transverse conductivity) based on microstructural attributes.

      PubDate: 2017-11-16T02:58:41Z
       
  • Interfacial polarization and dielectric properties of aligned carbon
           nanotubes/polymer composites: The role of molecular polarity
    • Abstract: Publication date: Available online 13 November 2017
      Source:Composites Science and Technology
      Author(s): Haibin Sun, Haolin Zhang, Suting Liu, Nanying Ning, Liqun Zhang, Min Tian, Yong Wang
      Dielectric elastomer (DE) composites have attracted much attention owing to their potential applications such as flexible electronics, energy storage, artificial muscles and sensors. The underlying mechanism to improve the electromechanical performance of DE is believed to be the interfacial polarization between fillers and matrix. Thus, understanding the interfacial polarization mechanism is a key to design and produce high performance DE composites. Despite of extensive works on studying the effect of fillers on interfacial polarization, the role of molecular polarity of matrix is still lacking. Thus, in this study, we prepared three kinds of carbon nanotubes (CNTs)/hydrogenated nitrile butadiene rubber (HNBR) DE composites with different molecular polarity of HNBR as the matrices and a special kind of aligned CNTs as the high dielectric constant (ε′) fillers to study the role of molecular polarity of HNBR on interfacial polarization and dielectric properties of the composites. These composites exhibit the similar dispersion and filler network of CNTs in matrices, which is a precondition of this study. Interestingly, at the same content of CNTs (higher than the percolation threshold), the ε′ of these composites largely increases with the enhancement of the molecular polarity of HNBR, whereas the ε′ of these pure HNBR matrices is very close. An equivalent circuit was then established to quantitatively analyze the interfacial polarization mechanism, and it fits well with the experiment data. This study demonstrates for the first time that the higher molecular polarity of matrix leads to the stronger interfacial polarization and thus results in higher ε′ of the composites.

      PubDate: 2017-11-16T02:58:41Z
       
  • High-strength boehmite-acrylate composites for 3D printing: Reinforced
           filler-matrix interactions
    • Abstract: Publication date: Available online 12 November 2017
      Source:Composites Science and Technology
      Author(s): Yanyang Han, FuKe Wang, Haimei Wang, Xiuling Jiao, Dairong Chen
      The development of additive manufacturing has offered great potential as well as challenge to resins with good performance. Here we report a facile strategy to obtain significant enhancement of mechanical properties for resins via incorporation of boehmite nanowires surface modified by a new modifier β-carboxyethyl acrylate (β-CEA), instead of the commonly used coupling agent 3-trimethoxysilylpropyl methacrylate (TMSPM). Fourier Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) characterizations were conducted to demonstrate the grafting of β-CEA onto the surface of boehmite nanowires. Significant mechanical enhancement was demonstrated by manufacturing and evaluation of product quality of delicate Fullerene model with neat acrylate and composite resins with β-CEA-AlOOH via Digital Light Processing (DLP) 3D printing.

      PubDate: 2017-11-16T02:58:41Z
       
  • The mechanics of reinforcement of polymers by graphene nanoplatelets
    • Abstract: Publication date: Available online 11 November 2017
      Source:Composites Science and Technology
      Author(s): Robert J. Young, Mufeng Liu, Ian A. Kinloch, Suhao Li, Xin Zhao, Cristina Vallés, Dimitrios G. Papageorgiou
      A detailed study has been undertaken of the mechanisms of stress transfer in polymeric matrices with different values of Young's modulus, E m, reinforced by graphene nanoplatelets (GNPs). For each material, the Young's modulus of the graphene filler, E f, has been determined using the rule of mixtures and it is found to scale with the value of E m. Additionally stress-induced Raman bands shifts for the different polymer matrices show different levels of stress transfer from the polymer matrix to the GNPs, which again scale with E m. A theory has been developed to predict the stiffness of the bulk nanocomposites from the mechanics of stress transfer from the matrix to the GNP reinforcement based upon the shear-lag deformation of individual graphene nanoplatelets. Overall it is found that it is only possible to realise the theoretical Young's modulus of graphene of 1.05 TPa for discontinuous nanoplatelets as E m approaches 1 TPa; the effective modulus of the reinforcement will always be less for lower values of E m. For flexible polymeric matrices the level of reinforcement is independent of the graphene Young's modulus and, in general, the best reinforcement will be obtained in nanocomposites with strong graphene-polymer interfaces and aligned nanoplatelets with high aspect ratios.

      PubDate: 2017-11-16T02:58:41Z
       
  • A micro-image based reconstructed finite element model of needle-punched
           C/C composite
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Jian Yu, Chuwei Zhou, Haijun Zhang
      A 3D microscopic FE approach of needle-punched carbon-carbon composite (NP C/C) is modeled based upon micro-CT technology. The images of micro-CT of NP C/C are processed and the outlines of warp, weft and punched fibre bundles are extracted. Then discrete gray images are generated and from them a microscopic FE model is reconstructed which can represent the features of micro structure and imperfections in NP C/C. Failure criterion and periodic boundary condition are employed in the FE approach and then progressive damages are investigated. Numerical simulation reveals the predominant failure mechanisms in this NP C/C under uniaxial tensile and compressive loads. The predicted stress/strain curves agree well with the experiment data.

      PubDate: 2017-10-14T01:51:33Z
       
  • A micromechanical model of interfacial debonding and elementary fiber
           pull-out for sisal fiber-reinforced composites
    • Abstract: Publication date: Available online 12 October 2017
      Source:Composites Science and Technology
      Author(s): Qian Li, Yan Li, Limin Zhou
      The interfacial failure behavior of sisal fiber-reinforced composites (SFRCs) was studied experimentally and theoretically. The residual pull-out strength of the SFRCs was observed to gradually decrease during the single sisal fiber pull-out test, after which the SFRCs presented multiple failure modes, including at the interface between technical fiber and matrix and at the interface between elementary fibers. To further investigate the failure mechanisms of SFRCs, using the traditional shear lag model, a double-interface model tailored to the unique multi-layer interface structure of plant fibers was developed to describe the fiber pull-out behavior and the interfacial adhesion status of single plant fiber-reinforced composites (PFRCs). By comparison with other existing models, using the experimental applied stress as reference, the proposed double-interface model was found to provide a more accurate quantitative theoretical prediction of the interfacial failure behavior of PFRCs during multi-stage fracture of the two interfaces.

      PubDate: 2017-10-14T01:51:33Z
       
  • A flexible and transparent thin film heater based on a carbon fiber
           /heat-resistant cellulose composite
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Pengbo Lu, Fan Cheng, Yanghao Ou, Meiyan Lin, Lingfeng Su, Size Chen, Xilang Yao, Detao Liu
      The thin flexible film heater made of carbon fibers is widely considered to be an ideal material for the use as self-heating devices because of its safe, low-cost, no noises, small size and fast heating as well as energy saving. Presently thin flexible film heater is mostly fabricated by mixing method using the long cellulose fibers as film-forming materials and carbon fibers as self-heating materials, which mostly suffer from opaque or uneven heating field. In this work, we firstly reported a flexible and transparent thin film heater (FTFH) composed of carbon fibers and regenerated cellulose. The use of regenerated cellulose for membrane materials brings high transmittance, strong adhesion, fast temperature response and high generated temperature. More importantly, the FTFH using novel carbon fibers as self-heating materials and regenerated cellulose as membrane materials show a rapid heating response (12 s), higher power density (2577 w/m2) and long-term stability of generated temperature (162.3 °C).

      PubDate: 2017-10-11T01:48:13Z
       
  • Multi-scaled carbon reinforcements in ternary epoxy composite materials:
           Dispersion and electrical impedance study
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): D. Baltzis, D.G. Bekas, G. Tzachristas, A. Parlamas, M. Karabela, N.E. Zafeiropoulos, A.S. Paipetis
      The following study, is focused on developing a ternary epoxy based composite material by the combined inclusion of two types of carbon fillers. The selected fillers (i.e. multi-walled carbon nano-tubes, MWCNTs and carbon black, CB), were dispersed using high speed shear mixing while the effect of dispersion duration, filler type and weight contents was studied using Impedance Spectroscopy (IS), fracture toughness tests and Dynamic Mechanical Thermal Analysis (DMTA). SEM was also employed in order to qualitatively assess the dispersion quality by means of mean agglomerate size and identify the fracture mechanisms. IS results indicated an inverse dependence between the magnitude of impedance and the dispersion duration. The decrease of the impedance with increasing dispersion duration was attributed to the formation of the conductive network. The synergistic effect between the two fillers was evident in the more rapid decrease in the maximum imaginary impedance values followed by a concurrent shift of the observed peaks towards higher frequencies with increasing dispersion duration. The synergy of the two fillers was also evident in the superior fracture toughness and thermomechanical performance of the ternary composites. The SEM micrographs revealed that the fracture surfaces of the ternary composites combined all the fracture mechanisms observed on the respective binary composites i.e. particle pull-out, crack bifurcation and pinning. DMTA revealed a significant increase in the storage modulus while glass transition temperature was marginally affected. Overall, the formation of the hybrid conductive network resulted in ternary composite materials with improved electric, mechanical and thermomechanical performance.
      Graphical abstract image

      PubDate: 2017-10-11T01:48:13Z
       
  • A micro-scale cutting model for UD CFRP composites with thermo-mechanical
           coupling
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Hui Cheng, Jiaying Gao, Orion Landauer Kafka, Kaifu Zhang, Bin Luo, Wing Kam Liu
      Cutting a unidirectional carbon fiber-reinforced polymer (UD CFRP) structure is the basic unit for CFRP machining, which is a complex thermal-mechanically coupled process. To reveal the deformation mechanism and predict cutting force in UD CFRP micro cutting, a micro-scale fracture model for UD CFRP cutting with thermal-mechanical coupling is demonstrated in this paper, which captures the failure modes for fibers, matrix and the interface based on a micro-level RVE using a relatively simple damage-based fracture method. The thermal-mechanical coupling model at the micro scale is developed on the basis of the plastic energy dissipation and frictional heating during cutting. Failure models for the fiber, matrix and interface region are applied depending on the material properties of each of these three phases. Numerical simulations based on the above model with different fiber orientations were performed to predict the deformation and forces of different components in UD CFRP. Cutting experiments with the same fiber orientations as considered in the simulations were carried out to validate the force and deformation results. The predicted force and deformation patterns match well with evidence from our experiments. In general, the cutting force is larger than the thrust force regardless of fiber orientation. The cutting force reaches a maximum as the fiber orientation approaches 90°, but thrust forces do not vary substantially across cases. When the fiber orientation is acute, the deformation of fibers is much smaller than when the cutting angle is obtuse. Surface roughness follows the same trend with cutting angle as fiber deformation.

      PubDate: 2017-10-11T01:48:13Z
       
  • A facile preparation route of n-type carbon buckypaper and its enhanced
           thermoelectric performance
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Jinmi Kim, O Hwan Kwon, Young Hun Kang, Kwang-Suk Jang, Song Yun Cho, Youngjae Yoo
      In this study, we prepared a thermoelectric device with p-type organic thermoelectric hybrid film and n-type buckypaper. Both the film and buckypaper are made of a hybrid filler of graphite nanoplatelets (GNPs) and single-walled carbon nanotubes (SWNTs). The p-type thermoelectric hybrid film has a free-standing form and enhanced thermoelectric performance owing to a polyvinylidene fluoride/carbon hybrid film purified with an acid solution, which successfully eliminates amorphous carbon, additives, and impurities. The n-type thermoelectric buckypaper was made with a filtration method with GNPs and SWNTs to the membrane filter. To convert this to an n-type thermoelectric property, a polyethyleneimine solution was also added by filtration process. In addition, adding sodium dodecyl benzene sulfonate during carbon dispersion enhanced thermoelectric performance, which was confirmed by measuring the electrical conductivity and Seebeck coefficient. A thermoelectric device using silver electrodes was produced with the thermoelectric composite film and buckypaper to verify its thermoelectric voltage and generating power.

      PubDate: 2017-10-11T01:48:13Z
       
  • Polymer/carbon nanotube composite materials for flexible thermoelectric
           power generator
    • Abstract: Publication date: Available online 9 October 2017
      Source:Composites Science and Technology
      Author(s): Haijun Song, Yang Qiu, Yao Wang, Kefeng Cai, Delong Li, Yuan Deng, Jiaqing He
      Flexible and lightweight thermoelectric (TE) generators have attracted increasing interest for powering wearable electronics using the temperature difference between human body and ambient air. Conducting polymers or their based composite materials are suitable for such applications; however, most conducting polymers show p-type conduction, hence, until now almost all reported flexible TE generators, which use conducting polymers or their based composite materials, are single-carrier-type (p-type) leg devices, connecting alternatively p-type legs electrically in series with silver or other metals. In this paper, both p- and n-type flexible TE materials have been developed using polymers and single-walled carbon nanotubes (SWCNTs). The p-type TE films are prepared by integrating SWCNTs into a high conductive poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) matrix, using a dilution-filtration method. N-type TE films with Seebeck coefficient about -35 μV/K are realized by treating SWCNTs with polyethyleneimine (PEI), and an encapsulation process has been employed to effectively preserve its n-type characteristics. Benefited from the flexibility of both the substrate and the composite films, a flexible TE prototype composed of six p-n junctions connected in series has been fabricated to demonstrate TE voltage output and power generation. The output power from the prototype is 220 nW for a 50 K temperature gradient.
      Graphical abstract image

      PubDate: 2017-10-11T01:48:13Z
       
  • Electric field assisted gradient structure formation of glass microsphere
           columns in polymer films
    • Abstract: Publication date: Available online 7 October 2017
      Source:Composites Science and Technology
      Author(s): Xueqing Liu, Jiyan Liu, Yuanhao Guo, Miko Cakmak
      Electric field-driven fabrication of gradient particle/polymer film was presented in current work. Direct-current (DC) field drives hollow glass microspheres (HGMs) to form microcolumns in UV-curable resin NOA65 by electrophoresis force and subsequently cured. In this field assisted alignment process, the microcolumns also exhibit gradient structure. The real-time organization of HGMs in the NOA65 was monitored during DC application by measuring the light transmission and taking photos with visible spectrometers and optical microscope respectively as the formation of column formation creates depletion zones between the columns leading to higher light transmission. The morphology evolved was found to depend on the electric field strength used and exposure time. The mechanical properties of the films produced by this process exhibit unique anisotropies when tested parallel and perpendicular to the electric field. When 10 phr HGMs in NOA65 undergoes 1000V/mm of DC for 0, 2, 4, 8 min respectively, the film obtained at 8 min shows highest storage modulus while the film obtained at 4 min shows highest modulus in compression mode.

      PubDate: 2017-10-11T01:48:13Z
       
  • Suppression of elevated temperatures space charge accumulation in
           polypropylene/elastomer blends by deep traps induced by surface-modified
           ZnO nanoparticles
    • Abstract: Publication date: Available online 7 October 2017
      Source:Composites Science and Technology
      Author(s): Bin Dang, Qi Li, Yao Zhou, Jun Hu, Jinliang He
      Space charge accumulation is a critical issue for the deterioration of the elevated temperature insulating property of polymeric materials. We present the influence of surface-modified ZnO nanoparticles on the space charge distribution and direct current (DC) resistivity of polypropylene (PP)/elastomer blends under elevated temperature. Octyltrimethoxysilane, a silane coupling agent, was used for the surface modification of nanoparticles. Morphology characterization results indicated that the elastomer and coated ZnO were well dispersed in the PP matrix. It was observed that the coated ZnO can significantly improve the insulating properties, including a minimized electric field distortion (4.0%) and increased DC volume resistivity (1.41 × 1018 Ω m) under an electric field of 40 kV/mm and 70 °C. The DC resistivity of 2 ph PP/elastomer/ZnO ternary composites was improved by 13.4 times compared with that of pure PP/elastomer blends. The suppression of space charges may originate from deep traps existing in spherulite boundaries and interfacial zones between polypropylene and ZnO. This work provides an effective method to endow a recyclable insulating material with outstanding elevated temperature insulating performances.

      PubDate: 2017-10-11T01:48:13Z
       
  • Preparation of NBR/Tannic acid composites by assembling a weak IPN
           structure
    • Abstract: Publication date: Available online 6 October 2017
      Source:Composites Science and Technology
      Author(s): Shuyan Yang, Wenjian Wu, Yuanqi Jiao, Zhuodi Cai, Hongbo Fan
      Sustainable self-reinforcement organic filler, which does not contribute to environmental pollution, has been realized in the rubber industry as an alternative to modifying inorganic fillers with coupling agents or preparing rubber fillers, such as carbon black, with petrochemical products that cause environmental problems. In this work, tannic acid (TA), the world's third largest class of plant components that are easily available, is used as a self-reinforcing organic filler to prepare nitrile–butadiene rubber/TA (NBR/T) composites. Results show that TA can melt partially under vulcanization to assemble a weak interpenetrating polymer network (IPN) structure by hydrogen bonds under cooling, which is responsible for the dramatic increase in the mechanical and flexible properties of NBR/T composites even at low TA dosage. This finding provides a new perspective in preparing high-performance and sustainable rubber composites without sacrificing fossil fuels or non-renewable environmental resources.

      PubDate: 2017-10-11T01:48:13Z
       
  • Assessing local yield stress and fracture toughness of carbon nanotube
           poly(methyl methacrylate) composite by nanosectioning
    • Abstract: Publication date: Available online 4 October 2017
      Source:Composites Science and Technology
      Author(s): F. Sun, U. Wiklund, F. Avilés, E.K. Gamstedt
      A nanosectioning (cutting) method was used to test the local shear yield stress and fracture toughness (specific work of surface formation) of multiwall carbon nanotube (MWCNT) poly(methyl methacrylate) (PMMA) composites, and the effect of MWCNT content on the stress and toughness were investigated. The composites were prepared by a solution casting method, with MWCNT content varying from 0.05 to 1.0 wt%. Above 0.1 wt% MWCNT content, the yield stress reduced by the addition of MWCNTs. The fracture toughness of the composite was effectively enhanced by the addition of MWCNTs, from 17 J/m2 for the neat PMMA to 25 J/m2 for the 1.0 wt% composite. The shear yield stresses obtained by nanosectioning were correlated to nanoindentation measurement, and possible contributions from the MWCNTs to the fracture toughness of the composite were analysed.

      PubDate: 2017-10-11T01:48:13Z
       
 
 
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